Investments (Distribution Of Securities By Contractual Maturity Of AFS and HTM) (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Fixed-Maturity Investments [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
Due in one year or less, Amortized Cost	$ 241
Due after one year through five years, Amortized Cost	1,044
Due after five years through ten years, Amortized Cost	770
Due after ten years through fifteen years, Amortized Cost	403
Due after fifteen years, Amortized Cost	1,048
Total available for sale, amortized cost	4,883
Due in one year or less, Fair Value	242
Due after one year through five years, Fair Value	1,061
Due after five years through ten years, Fair Value	803
Due after ten years through fifteen years, Fair Value	434
Due after fifteen years, Fair Value	1,137
Total available for sale, fair value	4,993
Fixed-Maturity Investments [Member] | Mortgage And Asset Backed Securities [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
Total available for sale, amortized cost	1,377
Total available for sale, fair value	1,316
Variable Interest Entity [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
Total held-to-maturity investments, Fair Value	2,674	3,489
Variable Interest Entity [Member] | Fixed-Maturity Investments [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
Due in one year or less, Amortized Cost	18
Due after one year through five years, Amortized Cost	113
Due after ten years through fifteen years, Amortized Cost	84
Total available for sale, amortized cost	427
Due in one year or less, Fair Value	18
Due after one year through five years, Fair Value	122
Due after ten years through fifteen years, Fair Value	81
Total available for sale, fair value	415
Due in one year or less, Amortized Cost
Due after one year through five years, Amortized Cost
Due after five years through ten years, Amortized Cost
Due after ten years through fifteen years, Amortized Cost
Due after fifteen years, Amortized Cost	2,829
Total held-to-maturity investments, Amortized Cost	2,829
Due in one year or less, Fair Value
Due after one year through five years, Fair Value
Due after five years through ten years, Fair Value
Due after ten years through fifteen years, Fair Value
Due after fifteen years, Fair Value	2,674
Total held-to-maturity investments, Fair Value	2,674
Variable Interest Entity [Member] | Fixed-Maturity Investments [Member] | Mortgage And Asset Backed Securities [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
Total available for sale, amortized cost	212
Total available for sale, fair value	$ 194